1. Field of the Invention
The invention relates to a high speed laboratory mixer including a test tube supporting cup means which translates in a circle path but does not rotate while the mixing operation takes place.
2. Description of the Prior Art
It is common practice in laboratories to work with large numbers of samples in small plastic test tubes. The plastic test tubes have many advantages over old fashioned glass tubes. Modern plastic tubes have their own covers, are unbreakable, solvent resistant and fit into small powerful centrifuges.
Mixing operations are normally carried out in these plastic tubes in the same manner as described in the prior art by U.S. Pat. No. 3,061,280. The mechanism described in U.S. Pat. No. 3,061,280 is believed to work well at slow speeds (below 3,000 revolutions per minute) but it is not believed to be capable of powerful high speed agitation. Many instances arise in a laboratory where the mixing of intractable substances is desirable. For example, bacteria centrigued down into the bottom of the plastic test tube can be quite tightly packed and resistant to dispersion by the type of mechanism described in U.S. Pat. No. 3,061,280. According to that invention an eccentricly mounted collar drives a resilient cup in a circular path. An arm connects the cup to an elongated spring which serves to dampen vibrations and to prevent the mixing cup from rotating. It is believed that the oscillatory, harmonic characteristics of the damping mechanism prevent the device from operating at high speeds in the neighborhood of 10,000 revolutions per minute. Moreover, there are no hand-rest switches for automatically triggering the operation of the mixing device through the hand pressure of the machine operator. The invention described in this disclosure is capable of safe operation at speeds in excess of 10,000 revolutions per minute. This type of agitation is necessary in order to disperse tightly packed bacteria, homogenized immiscible liquids or tissues and accomplish other difficult mixing procedures.
The device described in U.S. Pat. No. 3,159,384 has an advantage over the device described in U.S. Pat. No. 3,061,280 in that more than one tube can be agitated at the same time. However, it is also believed to be incapable of high speed use since it employs the same type of eccentric drive and spring retaining mechanism as is found in other prior art agitators. Moreover, it also does not include or suggest the use of a hand rest-switch to provide for comfortable one-hand operation.
The device described in U.S. Pat. No. 3,850,580 is similar to the devices described in U.S. Pat. Nos. 3,061,280 and 3,159,384 except that spring wire rod members are used to prevent rotation and provide damping in place of elongated coil springs.
U.S. Pat. No. 3,975,001 describes a mixer employing an eccentric drive to propell a gimbal mounted mixing cup cylinder. A test tube is inserted into the cylinder which includes a spring loaded cup in the bottom thereof. The intensity of the mixing action is controlled by the depth to which the test tube is inserted into the mixing cylinder against the pressure of the spring loaded cup. That device is different from the invention described in this disclosure in that high speed operation is not believed to be obtainable and there is no provision for hand rest-switching of the mechanism.
Other relevant prior art patents of lesser importance include: Nos. 982,156; 2,468,538; 2,480,502; 2,524,523; 2,846,201; 3,310,292; 3,346,241; 3,401,034; 3,768,634; 3,809,322; 4,042,218; 4,118,801 and 4,202,634.
Insofar as understood, none of the prior art references describe an efficient, reliable high speed agitator capable of actuation by a hand-rest switch thereby allowing convenient one-handed operation.